Field of the Invention
The present invention relates to a cooling device for a light source in a copying machine, and in particular to a cooling technology for a lighting device composed of a light source bulb and a reflector accommodated within a lamp body.
Generally, a high grade bright lamp such as a halogen lamp is utilized for lighting an original in a copying machine. However, such a bright lamp also radiates much heat, and elements near the lamp are apt to suffer from the resultant high temperature.
A known cooling device for a light source in a copying machine, as disclosed in Japanese Provisional Patent Publication No. 136322 of 1979, for example is so constructed that a duct-like lamp body which accommodates a long curved reflector and a light source bulb therein is provided with an irradiation opening and a filter that is pervious to light but blocking infrared rays. The air heated by the light source is removed by blowing air into the body so as to also cool the light source bulb.
However, since the filter that is a light-pervious heat-shield member is cooled only at the inside and the heat accumulated in it is radiated from its outer surface, elements near the filter can not be prevented from being heated thereby.
The heated air around the filter is therefore apt to appear waving with the heat radiated from the filter. When the seemingly waving air is extends into the light path focusing an image, in the optical system of the copying machine, the copied image is likely to be reproduced out of focus owing to the image focus being deteriorated by the "waving" heated air.